The goal of this proposal is to better characterize the effects of physical activity on stress responsiveness, and specifically adaptation to prolonged, repeated or chronic stress. It is the prolonged or repeated exposure to stressful life events that is most frequently associated with the development or precipitation of several psychiatric and physical disorders. Stress reduction has been suggested as an important factor in the beneficial effects of physical activity on several aspects of physical and mental health. Surprisingly, a majority of studies indicate that physical activity has no effect on, or even potentiates several major indices of acute stress, including the sympathetically-mediated release of arterial catecholamines, and the hypothalamo-pituitary-adrenocortical (HPA) axis-mediated release of glucocorticoids. In marked contrast, our preliminary rodent studies indicate that six weeks of moderate voluntary physical activity significantly facilitates glucocorticoid adaptation to repeated loud noise exposure, as compared to sedentary rats. This may be a critical observation in that some of the disease-promoting effects of stress are attributed to prolonged elevations of circulating glucocorticoid levels. These findings suggest that physical activity may significantly regulate the adaptive mechanisms triggered by stress without necessarily altering responsiveness to novel acute stress situations. Therefore, the primary working hypothesis to be tested in this proposal is that moderate physical activity facilitates chronic stress adaptation. Therefore, the specific Aims of the present proposal will determine: How much voluntary physical activity is necessary to produce facilitation of stress adaptation to repeated loud noise exposures, as indexed by circulating glucocorticoid levels (Aim 1); where and how physical activity regulates HPA axis function in response to chronic intermittent loud noise exposure (Aim 2); and the important question of whether physical activity-induced facilitation of stress adaptation generalizes to another stress situation (restraint), and to response systems other than the HPA axis (circulating catecholamines, heart rate, body temperature, and locomotor activity - Aim 3). [unreadable] [unreadable] [unreadable]